1,3,5,7-Tetraacetyl-1,3,5,7-octahydrotetrazocine (TAT) is an intermediate in a novel process for the production of the important military explosive HMX (1,3,5,7-tetranitro-1,3,5,7-octahydrotetrazocine), which is the subject of copending U.S. Pat. application, Ser. No. 445,738, filed Feb. 25, 1974, now U.S. Pat. No. 3,939,148, "Process For Preparing 1,3,5,7-Tetranitro-1,3,5,7-Tetraazacyclooctane," Victor I. Siele and Everett E. Gilbert, inventors. In the past TAT has been prepared by heating 1,5-diacetyl-1,3,5,7tetraazabicyclo (3,3,1) nonane (hereinafter referred to as DAPT) with acetic anhydride under anhydrous conditions, but the yields were always poor. Thus, G. C. Bassler, "The Chemistry of Cyclonite", Pennsylvania State University, PhD Thesis 1943, p. 179, obtained a 20% yield of TAT by heating DAPT with acetic anhydride containing a small amount of acetyl chloride at 95.degree.C. for 90 minutes. Attempts to improve the yield TAT by conducting the reaction in boiling chloroform solvent (b.p. 61.degree.C.) produced yields as high as 35% but the results were not reproducible.